With the advent of 10 Gigabit Ethernet and Fiber-to-the-Home (FTTH) with the Passive Optical Network (PON), residential user data rate is expected to exceed 100 Mb/s in the near future, and over 1 Gb/s in the long term, while enterprise users will enjoy 10 Gb/s connectivity. In addition, data-intensive users are expected to have 10 to 100 TB data sets to be delivered within 24 hours. To scale the Internet over existing network infrastructure, Dense Wavelength Division Multiplexing (DWDM) technology has made it possible to carry hundreds of wavelength channels over a single optical fiber at rates of 10 Gb/s and beyond. DWDM transmission has been widely deployed in long haul service provider networks, and is increasingly being deployed in metro service provider networks and for enterprise data center connectivity applications. In addition, WDM PON can deliver dedicated (unshared) bandwidth of over 1 Gb/s to residential users. DWDM has become the technology of choice for communication networks. While DWDM is universally used in transmission, different switching technologies can be used to direct input data to the output at router nodes. Current switching technologies can be characterized into electronic switching and optical switching technologies based on how data is processed in the router.
Electronic switching technology, also known as electronic packet switching (EPS), converts DWDM optical signals to electronic signals, and processes data (usually in the form of packets) electronically. After packets are routed to the destined output, they are converted back to an optical signal, and sent on DWDM links toward the downstream router. However, as the number of DWDM channels increases, the optical/electrical/optical (O/E/O) conversion required by electronic switching adds significantly to the overall system cost. For example, while it is technologically feasible to carry 512 wavelengths in a single optical fiber, it requires 512 O/E/O pairs in EPS routers, just to terminate a single DWDM link.
Optical switching technologies, on the other hand, allow DWDM channels to pass the router node optically, greatly reducing the cost to deploy DWDM channels over existing network infrastructure. Optical switching can be further divided into 3 technologies: a) Optical circuit switching (OCS), b) Optical packet switching (OPS), and c) Optical burst switching (OBS). In OCS, switching decisions are made at the wavelength level, and data passes through routers along pre-established lightpaths. Although the technology has been available for the past several years, its deployment has been slow due to its coarse granularity which limits its application in supporting dynamic traffic. OPS overcomes this limitation in that it is to switch packet level data optically. It is unlikely that OPS will be available in the foreseeable future, largely due to the lack of random access optical buffers, and the synchronization issues associated with the packet header and payload. OBS provides a granularity between optical circuit switching and optical packet switching. It allows the control header to establish an optical data path before data arrives at the optical switching fabric so that no optical buffer is needed. In addition, the decoupling of the control header and the data (burst) also bypasses the synchronization problem that OPS experiences. Currently, OBS is considered the most promising optical switching technology.
Unfortunately, there is no single switching technology that can scale cost-effectively with the number of DWDM channels while meeting the diverse needs of heterogeneous applications. Internet traffic may be heterogeneous, embracing all the data generated by applications that differ greatly in nature (e.g., VoIP, Video-on-Demand (VoD)), IPTV, 3G/WiMax, Virtual-Private-Network (VPN), and 10 Gigabit Ethernet). It seems that no single switching technology (EPS, OCS or OBS) can claim victory over all applications. Although optical switching technologies have advantages for scaling up DWDM systems, neither OCS nor OBS can switch at the packet level. However, fine packet level granularity is desirable when transporting short, latency sensitive messages, such as TCP (Transmission Control Protocol) acknowledgements. Even between the two optical switching technologies, OCS and OBS, it is hard to declare a winner for all types of applications. While it is clear that OBS performs well for most of bursty Internet traffic, OCS is more suitable for applications such as high energy physics that require sustained, long-term full channel bandwidth (i.e. 10 Gb/s and above). OCS is also a better fit for mission critical applications which cannot tolerate any data loss or delay. One can always build separate networks using different switching technologies to meet the respective needs of applications. However, for some applications, this implies a higher capital investment, separate management issues for each type of networks, and less flexibility; for others, unfortunately, there is no single type of network that can best fit the need for the application because of the characteristics of different types of messages within the application. Although attempts have been made to support specific applications in the network, none of them address the DWDM channel scaling issue.
In order to solve the dilemma, with both the applications and cost of system scaling in mind, an approach for traffic management in DWDM-based communication networks is discussed herein. The approach enables dynamic packet traffic management in DWDM networks.